Proton conductance of influenza virus M2 protein in planar lipid bilayers

Purified M2 protein from the Udorn strain of influenza virus was reconstituted into planar lipid bilayers from liposomes. In 1 mM HCl, the single-channel conductance was measured as 6 pS with open probability of less than or equal to0.03. The current voltage curve is linear over the achievable voltage range. The current amplitude is amantadine sensitive. In HCl solutions, the single-channel current was essentially invariant with changes in [Cl-], [Na+], and [ tetraethylammonium] ([TEA(+)]), but dependent on [H+]. The reversal potential, determined with asymmetrical hydrogen chloride solution, is very close to the equilibrium potential of hydrogen. This appears to be the first report of single-channel proton currents with the full-length M2 protein.